Dave Arquati wrote:
Aidan Stanger wrote:

Stephen Osborn wrote:

snip John Rowland wrote:

I think you are wrong there.

Contours mark places of equal height. If two contours touch at any one
point then, de definito, they have to touch at *all* points, so the two
contours become one contour.

You already have the counterexample of a vertical cliff. I have seen
those in nature - although not all of the cliff was vertical, there were
certainly parts that were, and they were definitely big and vertical
enough for contours to meet on the map.

I am still not convinced you will find a natural cliff that is *truly*
vertical (e.g. measured by a plumb line) for more than 10 metres, in
order to have the contour lines coincident.

I would be fascinated if you can think of an example where this is true.

For a travel map to be of use, every point on it has to share share the
same centre.


That statement is absolutely ridiculous!

Yes it is, isn't it. I had fallen into the same trap as Larry Lard (in
an earlier post) had and was thinking of the distance from the centre
showing the travelling time. Probably too much time looking at LU zonal
maps!

this would be referred to as isochromic isochrones!

Nice!

--

regards

Stephen

Stephen Osborn wrote:
I am still not convinced you will find a natural cliff that is *truly*
vertical (e.g. measured by a plumb line) for more than 10 metres, in
order to have the contour lines coincident.

I would be fascinated if you can think of an example where this is
true.

http://www.climbvertigo.ca/location-first-face.htm seems to indicate that in
places, the cliff is actually overhanging.

Tim (tm)
--
tim at economic-truth.co.uk Xbox Live gamertag: Xexyz
http://www.economic-truth.co.uk - the students' economics resource
http://www.ugvm.org.uk - the uk.games.video.misc magazine
The talkabout network is denied permission to reproduce this post

Tim Miller wrote:
Stephen Osborn wrote:

I am still not convinced you will find a natural cliff that is *truly*
vertical (e.g. measured by a plumb line) for more than 10 metres, in
order to have the contour lines coincident.

I would be fascinated if you can think of an example where this is
true.


http://www.climbvertigo.ca/location-first-face.htm seems to indicate that in
places, the cliff is actually overhanging.

Tim (tm)

Yes but that is not vertical so the contour lines (of different heights)
would not be coincident.

I am struggling to get my mind around how an overhang should be shown on
an OS map.

--

regards

Stephen

Stephen Osborn wrote:

http://www.climbvertigo.ca/location-first-face.htm seems to indicate
that in places, the cliff is actually overhanging.

Yes but that is not vertical so the contour lines (of different
heights) would not be coincident.

I am struggling to get my mind around how an overhang should be shown
on an OS map.

It would involve contour lines crossing. Each would have to be clearly
labelled at every point.

Tim (tm)
--
tim at economic-truth.co.uk Xbox Live gamertag: Xexyz
http://www.economic-truth.co.uk - the students' economics resource
http://www.ugvm.org.uk - the uk.games.video.misc magazine
The talkabout network is denied permission to reproduce this post